Stacked battery

ABSTRACT

An objective of the present disclosure is to provide a stacked battery that suppresses sneak current caused by an unevenness of a short circuit resistance among a plurality of cells. The present disclosure provides a stacked battery comprising: a plurality of cells in a thickness direction, wherein the plurality of cells are electrically connected in parallel; the stacked battery includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell; wherein a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; or a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.

TECHNICAL FIELD

The present disclosure relates to a stacked battery.

BACKGROUND ART

Stacked batteries comprising a plurality of cells in a thicknessdirection are known; wherein each of the plurality of cells includes acathode current collector, a cathode active material layer, a solidelectrolyte layer, an anode active material layer, and an anode currentcollector, in this order. For example, Patent Literature 1 discloses alithium ion secondary battery comprising a plurality of unit cells,wherein each of the plurality of unit cells includes: a cathode layerprovided with a cathode current collector and a cathode mixture layer; asolid electrolyte layer; and an anode layer provided with an anodecurrent collector and an anode mixture layer. Further, Patent Literature1 discloses a nail penetration test as a method for evaluating thesafety of all solid batteries.

Also, for example, Patent Literature 2 discloses a method for producinga stacked type all solid battery wherein: the stacked type all solidbattery comprises a plurality of all solid battery cells connected in abipolar form or in a monopolar form; and each of the plurality of allsolid battery cells includes a cathode current collector layer, acathode active material layer, a solid electrolyte layer, an anodeactive material layer, and an anode current collector layer. Also, forexample, Patent Literature 3 discloses a secondary battery wherein atleast either widths or thicknesses of the current collector leads arevaried according to the length of the current collector lead connectedto a stacked body among a plurality of stacked bodies.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Patent Application Laid-Open (JP-A) No.2016-207614

Patent Literature 2: JP-A No. 2016-136490

Patent Literature 3: JP-A No. 2012-181941

SUMMARY OF DISCLOSURE Technical Problem

As described above, the nail penetration test is known as a method forevaluating the safety of all solid batteries. The nail penetration testis a test of penetrating a conductive nail through an all solid battery,and observing changes (such as a temperature change) when an internalshort circuit within the battery occurs.

From detailed studies of the nail penetration test of stacked batteriescomprising a plurality of all solid battery cells electrically connectedin parallel, the present inventors have acquired new knowledge that theresistance of a short circuit part (short circuit resistance) in eachcell varies greatly with the cell location. When a cell with low shortcircuit resistance and a cell with high short circuit resistance aremixed, a current flows from the cell with high short circuit resistanceinto the cell with low short circuit resistance. Hereinafter, this maybe referred to as a “sneak current”. When the sneak current occurs, thetemperature of the cell with low short circuit resistance (the cell towhich the current flowed into) increases, and as the result, the batterymaterials are easily deteriorated.

The present disclosure has been made in view of the above circumstances,and a main object thereof is to provide a stacked battery in which sneakcurrent caused by an unevenness of a short circuit resistance among aplurality of cells, is suppressed.

Solution to Problem

In order to achieve the object, the present disclosure provides astacked battery comprising: a plurality of cells in a thicknessdirection, wherein the plurality of cells are electrically connected inparallel; each of the plurality of cells includes a cathode currentcollector with a cathode current collecting tab, a cathode activematerial layer, a solid electrolyte layer, an anode active materiallayer, and an anode current collector with an anode current collectingtab, in this order; the stacked battery includes a surface-side cellthat is located on a surface side of the stacked battery, and acenter-side cell that is located on a center side rather than thesurface-side cell; and the surface-side cell and the center-side cellsatisfy at least one of:

condition i) a resistance of the cathode current collecting tab in thesurface-side cell is more than a resistance of the cathode currentcollecting tab in the center-side cell; and condition ii) a resistanceof the anode current collecting tab in the surface-side cell is morethan a resistance of the anode current collecting tab in the center-sidecell.

According to the present disclosure, since the surface-side cell and thecenter-side cell satisfy at least one of condition i) and condition ii),sneak current caused by an unevenness of a short circuit resistanceamong a plurality of cells, may be suppressed in a stacked battery.

In the disclosure, a specific resistance of the cathode currentcollecting tab in the surface-side cell may be more than a specificresistance of the cathode current collecting tab in the center-sidecell.

In the disclosure, a specific resistance of the anode current collectingtab in the surface-side cell may be more than a specific resistance ofthe anode current collecting tab in the center-side cell.

In the disclosure, a thickness of the cathode current collecting tab inthe surface-side cell may be less than a thickness of the cathodecurrent collecting tab in the center-side cell.

In the disclosure, a thickness of the anode current collecting tab inthe surface-side cell may be less than a thickness of the anode currentcollecting tab in the center-side cell.

In the disclosure, an area of the cathode current collecting tab in thesurface-side cell may be less than an area of the cathode currentcollecting tab in the center-side cell.

In the disclosure, an area of the anode current collecting tab in thesurface-side cell may be less than an area of the anode currentcollecting tab in the center-side cell.

In the disclosure, the cathode current collecting tab in thesurface-side cell may include a resistor on at least one surface side.

In the disclosure, the anode current collecting tab in the surface-sidecell may include a resistor on at least one surface side.

In the disclosure, an area of a welded portion in contact with thecathode current collecting tab in the surface-side cell may be less thanan area of a welded portion in contact with the cathode currentcollecting tab in the center-side cell.

In the disclosure, an area of a welded portion in contact with the anodecurrent collecting tab in the surface-side cell may be less than an areaof a welded portion in contact with the anode current collecting tab inthe center-side cell.

In the disclosure, when each of the plurality of cells is numbered as1^(st) cell to N^(th) cell, in which N≥3, in order along the thicknessdirection of the stacked battery, the surface-side cell may be a cellthat belongs to a cell region A including 1^(st) cell to (N/3)^(th)cell.

In the disclosure, the center-side cell may be a cell that belongs to acell region B including ((N/3)+1)^(th) cell to (2N/3)^(th) cell.

In the disclosure, an average resistance of the cathode currentcollecting tab in the cell region A may be more than an averageresistance of the cathode current collecting tab in the cell region B.

In the disclosure, an average resistance of the anode current collectingtab in the cell region A may be more than an average resistance of theanode current collecting tab in the cell region B.

In the disclosure, when each of the plurality of cells is numbered as1^(st) cell to N^(th) cell, in which N≥60, in order along the thicknessdirection of the stacked battery, the surface-side cell may be a cellthat belongs to a cell region C including 1^(st) cell to 20^(th) cell.

In the disclosure, the center-side cell may be a cell that belongs to acell region D including 21^(st) cell to 40^(th) cell.

In the disclosure, an average resistance of the cathode currentcollecting tab in the cell region C may be more than an averageresistance of the cathode current collecting tab in the cell region D.

In the disclosure, an average resistance of the anode current collectingtab in the cell region C may be more than an average resistance of theanode current collecting tab in the cell region D.

In the disclosure, the anode active material layer may include Si or aSi alloy as an anode active material.

Advantageous Effects of Disclosure

The stacked battery in the present disclosure effects that sneak currentcaused by an unevenness of a short circuit resistance among a pluralityof cells, is suppressed.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic cross-sectional view showing an example of thestacked battery of the present disclosure.

FIG. 2 is a schematic cross-sectional view explaining a nail penetrationtest.

FIG. 3 is a graph showing the relationship between the cell location andthe short circuit resistance.

FIG. 4 is an equivalent circuit explaining a sneak current.

FIG. 5 is a schematic cross-sectional view explaining a nail penetrationtest.

FIG. 6 is a schematic perspective view exemplifying the currentcollector in the present disclosure.

FIGS. 7A to 7D are schematic perspective views exemplifying the currentcollecting tab in the present disclosure.

FIGS. 8A to 8E are schematic cross-sectional views exemplifying a methodfor producing a two-stacked cell.

FIG. 9 is a graph exemplifying a voltage profile in a nail penetrationtest.

DESCRIPTION OF EMBODIMENTS

The stacked battery of the present disclosure will be hereinafterdescribed in detail. FIG. 1 is a schematic cross-sectional view showingan example of the stacked battery of the present disclosure. Stackedbattery 100 shown in FIG. 1 comprises plurality of cells 10 (10A, 10B to10H to 10N) in a thickness direction; and each of plurality of cells 10includes cathode current collector 4 with a cathode current collectingtab, cathode active material layer 1, solid electrolyte layer 3, anodeactive material layer 2, and anode current collector 5 with an anodecurrent collecting tab, in this order. Further, plurality of cells 10are electrically connected in parallel. A method for connecting thecells in parallel is not particularly limited, and for example, cell 10Aand cell 10B shown in FIG. 1 are connected in parallel in a manner thatthe cells share anode current collector 5. Incidentally, two cells nextto each other may or may not share cathode current collector 4 or anodecurrent collector 5. In the latter case, for example, by providingtwo-layered cathode current collector 4 or two-layered anode currentcollector 5, the two cells next to each other have cathode currentcollector 4 or anode current collector 5 individually between the cells.

Also, stacked battery 100 includes surface-side cell 10X that is locatedon a surface side of stacked battery 100, and center-side cell 10Y thatis located on a center side rather than surface-side cell 10X. Further,surface-side cell 10X and center-side cell 10Y feature a configurationthey satisfy at least one of:

condition i) a resistance of the tab of cathode current collector 4(cathode current collecting tab) in surface-side cell 10X is more than aresistance of the tab of cathode current collector 4 (cathode currentcollecting tab) in center-side cell 10Y; and condition ii) a resistanceof the tab of anode current collector 5 (anode current collecting tab)in surface-side cell 10X is more than a resistance of the tab of anodecurrent collector 5 (anode current collecting tab) in center-side cell10Y.

According to the present disclosure, since the surface-side cell and thecenter-side cell satisfy at least one of condition i) and condition ii),sneak current caused by an unevenness of a short circuit resistanceamong a plurality of cells, may be suppressed in the stacked battery. Asdescribed above, from detailed studies of the nail penetration test ofstacked batteries comprising a plurality of cells electrically connectedin parallel, the present inventors have acquired new knowledge that theresistance of a short circuit part (short circuit resistance) in eachcell varies greatly with the cell location.

This new knowledge will be explained referring to FIG. 2. As shown inFIG. 2, nail 110 is penetrated into stacked battery 100 comprisingplurality of cells 10 (10A, 10B to 10H to 10N) electrically connected inparallel. On this occasion, short circuit resistance R (R_(A), R_(B) toR_(H) to R_(N)) is determined with respect to each cell 10. As theresult of such detailed studies, as shown in FIG. 3 for example, it wasfound out that cell 10A located on the surface side has lower shortcircuit resistance compared to cell 10H located on the center side. Inother words, it was found out that there was the unevenness of shortcircuit resistance among the plurality of cells.

When a cell with low short circuit resistance and a cell with high shortcircuit resistance are mixed, a current flows from the cell with highshort circuit resistance into the cell with low short circuitresistance. As shown in FIG. 4 for example, when a short circuit occurswithin a stacked battery comprising cell 10A and cell 10H electricallyconnected in parallel in which short circuit resistance R_(A) of cell10A is lower than short circuit resistance R_(H) of cell 10H, sneakcurrent I flowing from cell 10H into cell 10A occurs in accordance withOhm's law. When sneak current I occurs, the temperature of cell 10Arises due to Joule heating; as the result, the deterioration of thebattery material easily occurs.

Although the reason why the unevenness of short circuit resistanceexists among the plurality of cells is not completely clear, it ispresumed as follows. As shown in FIG. 5 for example, on the surface side(such as location P₁ in FIG. 3) of the stacked battery, by penetratingnail 110 into cell 10, a state in which cathode current collector 4 andanode current collector 5 are in contact, and a state in which cathodeactive material layer 1 and anode current collector 5 are in contact,are presumed to occur.

Meanwhile, on the center side (such as location P₂ in FIG. 3) of thestacked battery, since the nail proceeds while dragging the fragment ofeach member, a state in which the cathode current collector and theanode current collector are not in contact, and a state in which thecathode active material layer and the anode current collector are not incontact, are presumed to occur. For the “state not in contact”, forexample, the following states may be supposed: a state in which thefragment of the solid electrolyte layer exists between the two, and astate in which a void exists between the two. As the result, the shortcircuit resistance will be higher on the center side of the stackedbattery.

Incidentally, the behavior of the short circuit resistance on thesurface side that is opposite to the nail penetrating surface (such aslocation P₃ in FIG. 3) of the stacked battery may possibly vary with theconstitution of the stacked battery; however, in both of the laterdescribed Reference Examples 1 and 2, the short circuit resistance waslowered. The reason therefor is presumed that, since the nail proceedswhile dragging the larger amount of the fragment of each member, thecathode current collector and the anode current collector will be in astate electrically connected by the fragment with high electronconductivity.

In contrast, in the present disclosure, since the surface-side cell andthe center-side cell satisfy at least one of condition i) and conditionii), sneak current caused by an unevenness of a short circuit resistanceamong a plurality of cells, may be suppressed in the stacked battery.Specifically, by using a current collecting tab with relatively highresistance for the surface-side cell with low short circuit resistance,and using a current collecting tab with relatively low resistance forthe center-side cell with high short circuit resistance, sneak currentmay be suppressed by the difference of the resistance of the currentcollecting tabs even when the sneak current caused by an unevenness of ashort circuit resistance among a plurality of cells occurs.Incidentally, in the present disclosure, an inclusive term of merely“current collecting tab” may be used for a cathode current collectingtab and an anode current collecting tab.

Also, the problem of suppressing the sneak current caused by anunevenness of a short circuit resistance among a plurality of cells is aproblem never occurs in a single cell, that is, a problem peculiar to astacked battery. Further, in a typical all-solid-type stack battery,since all of the constituting members are solids, a pressure applied tothe stacked battery during a nail penetration test will be extremelyhigh. Since a high pressure such as 100 MPa or more at the part wherethe nail penetrates, and particularly, 400 MPa or more at the tip partof the nail, is applied, the management of the short circuit resistancein a high pressure condition is important. In contrast, in aliquid-based battery, since a void into where the liquid electrolytepenetrates exists in the electrode, a pressure applied to the batteryduring a nail penetration test will be greatly lower. That is, it isdifficult to conceive of managing the short circuit resistance in a highpressure condition, based on the technique of the liquid-based battery.

1. Resistance of Current Collecting Tab

The stacked battery of the present disclosure includes a surface-sidecell that is located on a surface side of the stacked battery, and acenter-side cell that is located on a center side rather than thesurface-side cell. Further, the surface-side cell and the center-sidecell satisfy at least one of: condition i) a resistance of the cathodecurrent collecting tab in the surface-side cell is more than aresistance of the cathode current collecting tab in the center-sidecell; and condition ii) a resistance of the anode current collecting tabin the surface-side cell is more than a resistance of the anode currentcollecting tab in the center-side cell.

The stacked battery of the present disclosure usually satisfies at leastone condition of: including two kinds or more of the cathode currentcollecting tabs with a different resistance, and including two kinds ormore of the anode current collecting tabs with a different resistance.Here, “surface-side cell” and “center-side cell” in the presentdisclosure are stipulations for specifying the current collecting tabswith a different resistance. For example, an assumed case is a stackedbattery including two kinds of the cathode current collecting tabs(cathode current collecting tab α and cathode current collecting tab β)with a different resistance. Incidentally, the resistances are cathodecurrent collecting tab α>cathode current collecting tab β. When aplurality of cells including the cathode current collecting tab α existon the surface side of the stacked battery, any one of the plurality ofcells may be specified as the surface-side cell. Meanwhile, when aplurality of cells including the cathode current collecting tab β existon the center side of the stacked battery, any one of the plurality ofcells may be specified as the center-side cell. Also, for example, whenthe stacked battery includes three kinds or more of the cathode currentcollecting tabs with a different resistance, comparing two cathodecurrent collecting tabs with a different resistance among them, when themagnitude relation of the resistances and the locational relation of thetwo cathode current collecting tabs (cells) satisfy the specificconditions, the cell including one cathode current collecting tab isspecified as the surface-side cell, and the cell including the othercathode current collecting tab is specified as the center-side cell.Incidentally, although the explanation was made exemplifying the cathodecurrent collecting tab, it is much the same for the anode currentcollecting tab.

When the resistance of the cathode current collecting tab in thesurface-side cell is regarded as R₁ and the resistance of the cathodecurrent collecting tab in the center-side cell is regarded as R₂, thevalue of R₁/R₂ is, for example, 1.1 or more, and may be 10 or more.Meanwhile, the value of R₁/R₂ is, for example, 200 or less. Similarly,when the resistance of the anode current collecting tab in thesurface-side cell is regarded as R₃ and the resistance of the anodecurrent collecting tab in the center-side cell is regarded as R₄, apreferable range of R₃/R₄ is similar to that of R₁/R₂. The resistance ofthe cathode current collecting tab and the anode current collecting tabmay be obtained from, for example, the specific resistance and the shapethereof.

In the present disclosure, the resistance of the cathode currentcollecting tab in the surface-side cell is preferably more than theresistance of the cathode current collecting tab in the center-sidecell. Similarly, in the present disclosure, the resistance of the anodecurrent collecting tab in the surface-side cell is preferably more thanthe resistance of the anode current collecting tab in the center-sidecell. Also, examples of a current collector with a current collectingtab may include, as shown in FIG. 6, current collector 50 includingelectrode contacting part S that comes into contact with an electrodeand current collecting tab T in the form of a projection that projectsfrom a side of electrode contacting part S. The resistance of thecurrent collecting tab may be adjusted, for example, by the propertiesof the current collecting tab, a shape of the current collecting tab, aplacement of a resistor, and a welding condition.

(1) Property of Current Collecting Tab

A specific resistance of the cathode current collecting tab in thesurface-side cell may be more than a specific resistance of the cathodecurrent collecting tab in the center-side cell. Similarly, a specificresistance of the anode current collecting tab in the surface-side cellmay be more than a specific resistance of the anode current collectingtab in the center-side cell. When the material of the current collectingtab differs, the specific resistance also differs. The specificresistances of the materials used for the current collecting tab areexemplified in Table 1.

TABLE 1 Specific Resistance (10⁻⁶Ω · cm) Al 2.65 Cu 1.72 Fe 9.7 SUS 72Ti 55

In the surface-side cell and the center-side cell, the cathode currentcollecting tabs may contain the same material whereas the anode currentcollecting tabs may contain different materials; the cathode currentcollecting tabs may contain different materials whereas the anodecurrent collecting tabs may contain the same material; and both of thecathode current collecting tabs and the anode current collecting tabsmay contain different materials. Incidentally, the current collectingtab is typically formed continuously from the electrode contacting part.That is, the electrode contacting part and the current collecting tabtypically include the same material.

(2) Shape of Current Collecting Tab

A thickness of the cathode current collecting tab in the surface-sidecell may be less than a thickness of the cathode current collecting tabin the center-side cell. Similarly, a thickness of the anode currentcollecting tab in the surface-side cell may be less than a thickness ofthe anode current collecting tab in the center-side cell. For example,as shown in FIG. 7A, the thickness of current collecting tab T_(X) inthe surface-side cell may be less than the thickness of currentcollecting tab T_(Y) in the center-side cell. When the thickness of thecurrent collecting tab is larger, the resistance of the currentcollecting tab tends to be lower. The difference of the thicknesses is,for example, 30 μm or more, and may be 200 μm or more.

In the surface-side cell and the center-side cell, the cathode currentcollecting tabs may contain the same material whereas the thickness ofthe cathode current collecting tabs may be different; and the cathodecurrent collecting tabs may contain different materials as well as thethickness of the cathode current collecting tabs may be different.Similarly, in the surface-side cell and the center-side cell, the anodecurrent collecting tabs may contain the same material whereas thethickness of the anode current collecting tabs may be different; and theanode current collecting tabs may contain different materials as well asthe thickness of the anode current collecting tabs may be different.

An area of the cathode current collecting tab in the surface-side cellmay be less than an area of the cathode current collecting tab in thecenter-side cell. Similarly, an area of the anode current collecting tabin the surface-side cell may be less than an area of the anode currentcollecting tab in the center-side cell. For example, as shown in FIG.7B, the area (the area in plan view) of current collecting tab T_(X) inthe surface-side cell may be less than the area of current collectingtab T_(Y) in the center-side cell. When the area of the currentcollecting tab is larger, the resistance of the current collecting tabtends to be lower. Incidentally, in FIG. 7B, current collecting tabT_(X) and current collecting tab T_(Y) have the same length in depthdirection D; however, have different length in width direction W. Theproportion of the area of the current collecting tab T_(Y) in thecenter-side cell with respect to the area of the current collecting tabT_(X) in the surface-side cell is, for example, 1.2 or more, and may be2 or more. Meanwhile, the proportion is, for example, 10 or less.

For example, when the material of the current collecting tabs (cathodecurrent collecting tab and anode current collecting tab) in thesurface-side cell and the center-side cell are the same, the resistanceof the current collecting tabs may be adjusted by the shapes of thecurrent collecting tabs.

(3) Placement of Resistor

The cathode current collecting tab in the surface-side cell may includea resistor on at least one surface side. Similarly, the anode currentcollecting tab in the surface-side cell may include a resistor on atleast one surface side. For example, as shown in FIG. 7C, currentcollecting tab T_(X) in the surface-side cell may include resistor 20 onat least one surface side. Incidentally, in FIG. 7C, current collectingtab T_(Y) in the center-side cell does not include resistor 20. Byproviding the resistor, the resistance of the current collecting tabtends to be high. The material of the resistor and the material of thecurrent collecting tab in the surface-side cell may be the same, or maybe different. In the latter case, the specific resistance of theresistor is preferably more than the specific resistance of the currentcollecting tab in the surface-side cell.

For example, when the material and the shape of the current collectingtabs (cathode current collecting tab and anode current collecting tab)in the surface-side cell and the center-side cell are the same, theresistance of the current collecting tabs may be adjusted by placing theresistor.

(4) Welding Condition

An area of a welded portion in contact with the cathode currentcollecting tab in the surface-side cell may be less than an area of awelded portion in contact with the cathode current collecting tab in thecenter-side cell. Similarly, an area of a welded portion in contact withthe anode current collecting tab in the surface-side cell may be lessthan an area of a welded portion in contact with the anode currentcollecting tab in the center-side cell. For example, as shown in FIG.7D, the area of welded portion 21 in contact with cathode currentcollecting tab T_(X) in the surface-side cell may be less than the areaof welded portion 21 in contact with cathode current collecting tabT_(y) in the center-side cell. Incidentally, in FIG. 7D, a plurality ofwelded portions 21 are formed on the end face of the current collectingtab. Also, although current collecting tabs T_(X) and T_(Y) haveresistors 20 in FIG. 7D, resistors 20 may not be provided.

For example, when the material and the shape of the current collectingtabs (cathode current collecting tab and anode current collecting tab)in the surface-side cell and the center-side cell are the same, theresistance of the current collecting tabs may be adjusted by the area ofthe welded portion.

2. Constitution of Stacked Battery

Each of the plurality of cells included in the stacked battery isnumbered as a 1^(st) cell to a N^(th) cell in order along the thicknessdirection of the stacked battery. N refers to the total cell numberincluded in the stacked battery; for example, N is 3 or more, may be 10or more, may be 20 or more, and may be 40 or more. Meanwhile, N is, forexample, 200 or less, may be 150 or less, and may be 100 or less.

The surface-side cell is preferably a cell that belongs to a cell regionincluding the 1^(st) cell to a (N/3)^(th) cell. Here, the (N/3)^(th)cell is a cell whose order corresponds to a value obtained by dividingthe total cell number N by three. For example, when the total cellnumber is 60, the (N/3)^(th) cell is a 20^(th) cell. Incidentally, whenthe (N/3) is not an integer, the (N/3)^(th) cell is specified byrounding off to the nearest integer. Also, the surface-side cell may be,for example, a cell that belongs to a cell region including the 1^(st)cell to the 20^(th) cell, and may be a cell that belongs to a cellregion including the 1^(st) cell to a 10^(th) cell.

Also, the surface-side cell may be, for example, a cell that belongs toa cell region including a 5^(th) cell to the (N/3)^(th) cell, and may bea cell that belongs to a cell region including the 10^(th) cell to the(N/3)^(th) cell. As mentioned in the later described Reference Examples1 and 2, due to the influence of an exterior package such as a laminatefilm, the short circuit resistance of the 1^(st) cell during a nailpenetration may be high in some cases. Therefore, the surface-side cellmay be specified, excluding the 1^(st) cell and the neighborhood cells.

Meanwhile, the center-side cell is a cell that is located on the centerside rather than the surface-side cell. “Center side” refers to thecentral side in the thickness direction of the stacked cells. Thecenter-side cell is preferably a cell that belongs to a cell regionincluding a ((N/3)+1)^(th) cell to a (2N/3)^(th) cell. Here, the((N/3)+1)^(th) cell refers to a cell next to the (N/3)^(th) cell whennumbered from the 1^(st) cell. Meanwhile, the (2N/3)^(th) cell is a cellwhose order corresponds to a value obtained by dividing the doubledvalue of the total cell number N by three. For example, when the totalcell number is 60, the (2N/3)^(th) cell is a 40^(th) cell. Incidentally,when the (2N/3) is not an integer, the (2N/3)^(th) cell is specified byrounding off to the nearest integer. Also, the center-side cell may be,for example, a cell that belongs to a cell region including the 21^(st)cell to the 40^(th) cell.

Also, a cell region including the 1^(st) cell to the (N/3)^(th) cell isregarded as a cell region A, and a cell region including the((N/3)+1)^(th) cell to the (2N/3)^(th) cell is regarded as a cell regionB. The average resistance R_(AC) of the cathode current collecting tabin the cell region A is preferably more than the average resistanceR_(BC) of the cathode current collecting tab in the cell region B. Thevalue of R_(AC)/R_(BC) is, for example, 1.1 or more, and may be 10 ormore. Meanwhile, the value of R_(AC)/R_(BC) is, for example, 200 orless. Similarly, the average resistance R_(AA) of the anode currentcollecting tab in the cell region A is preferably more than the averageresistance R_(BA) of the anode current collecting tab in the cell regionB. The preferable range of R_(AA)/R_(BA) is similar to that ofR_(AC)/R_(BC).

Also, a cell region including the 1^(st) cell to the 20^(th) cell isregarded as a cell region C, and a cell region including the 21^(st)cell to the 40^(th) cell is regarded as a cell region D. The averageresistance R_(CC) of the cathode current collecting tab in the cellregion C is preferably more than the average resistance R_(DC) of thecathode current collecting tab in the cell region D. The value ofR_(CC)/R_(DC) is, for example, 1.1 or more, and may be 10 or more.Meanwhile, the value of R_(CC)/R_(DC) is, for example, 200 or less.Similarly, the average resistance R_(CA) of the anode current collectingtab in the cell region C is preferably more than the average resistanceR_(DA) of the anode current collecting tab in the cell region D. Thepreferable range of R_(CA)/R_(DA) is similar to that of R_(CC)/R_(DC).

Also, in the stacked battery after a nail penetration test, theresistance of the cell with the lowest total of the short circuitresistance and the tab resistance is regarded as R_(Min), and theresistance of the cell with the highest total of the short circuitresistance and the tab resistance is regarded as R_(Max). For example,when a metal active material (particularly Si or an Si alloy) is used asthe anode active material, the value of R_(Max)/R_(Min) is preferably100 or less, and more preferably 5.0 or less. Incidentally, the nailpenetration test is carried out under conditions mentioned in the laterdescribed Reference Examples 1 and 2.

3. Cell

The cell in the present disclosure includes a cathode current collector,a cathode active material layer, a solid electrolyte layer, an anodeactive material layer, and an anode current collector, in this order.The cell is typically a cell utilizing Li ion conductivity (a Li ioncell). Also, the cell is preferably a cell capable of being charged anddischarged (a secondary battery).

(1) Anode Active Material Layer

The anode active material layer includes at least an anode activematerial, and may include at least one of a solid electrolyte material,a conductive material, and a binder as required.

The anode active material is not particularly limited, and examplesthereof may include a metal active material, a carbon active material,and an oxide active material. Examples of the metal active material mayinclude a simple substance of metal and a metal alloy. Examples of themetal element included in the metal active material may include Si, Sn,In, and Al. The metal alloy is preferably an alloy including the abovedescribed metal element as the main component. Examples of the Si alloymay include a Si—Al base alloy, a Si—Sn base alloy, a Si—In base alloy,a Si—Ag base alloy, a Si—Pb base alloy, a Si—Sb base alloy, a Si—Bi basealloy, a Si—Mg base alloy, a Si—Ca base alloy, a Si—Ge base alloy, and aSi—Pb base alloy. Incidentally, the Si—Al based alloy, for example,refers to an alloy including at least Si and Al, may be an alloyincluding only Si and Al, and may be an alloy further including anadditional metal element. It is much the same for the alloys other thanthe Si—Al based alloy. The metal alloy may be a two-component basedalloy, and may be a multicomponent based alloy including three or morecomponents.

Meanwhile, examples of the carbon active material may include amesocarbon microbead (MCMB), a highly oriented pyrolytic graphite(HOPG), a hard carbon, and a soft carbon. Also, examples of the oxideactive material may include a lithium titanate such as Li₄Ti₅O₁₂.

Examples of the shape of the anode active material may include agranular shape. The average particle size (D₅₀) of the anode activematerial is, for example, within a range of 10 nm to 50 μm, and may bewithin a range of 100 nm to 20 μm. The proportion of the anode activematerial in the anode active material layer is, for example, 50% byweight or more, and may be within a range of 60% by weight to 99% byweight.

The solid electrolyte material is not particularly limited, and examplesthereof may include an inorganic solid electrolyte material such as asulfide solid electrolyte material, and an oxide solid electrolytematerial. Examples of the sulfide solid electrolyte material may includeLi₂S—P₂S₅, Li₂S—P₂S₅—LiI, Li₂S—P₂S₅—LiI—LiBr, Li₂S—P₂S₅—Li₂O,Li₂S—P₂S₅—Li₂O—LiI, Li₂S—SiS₂, Li₂S—SiS₂—LiI, Li₂S—SiS₂—LiBr,Li₂S—SiS₂—LiCl, Li₂S—SiS₂—B₂S₃—LiI, Li₂S—SiS₂—P₂S₅—LiI, Li₂S—B₂S₃,Li₂S—P₂S₅—ZmSn (wherein m and n are respectively a positive number; Z isany one of Ge, Zn, and Ga.), Li₂S—GeS₂, Li₂S—SiS₂—Li₃PO₄,Li₂S—SiS₂—Li_(x)MO_(y) (wherein x and y are respectively a positivenumber; M is any one of P, Si, Ge, B, Al, Ga, and In.) Incidentally, theabove described “Li₂S—P₂S₅” refers to a sulfide solid electrolytematerial using a raw material composition including Li₂S and P₂S₅, andit is much the same for other descriptions.

In particular, the sulfide solid electrolyte material is preferablyprovided with an ion conductor including Li, A (A is at least one kindof P, Si, Ge, Al, and B), and S. Further, the ion conductor preferablyincludes an anion structure (PS₄ ³⁻ structure, SiS₄ ⁴⁻ structure, GeS₄⁴⁻ structure, AlS₃ ³⁻ structure, BS₃ ³⁻ structure) of anortho-composition, as the main component of an anion. The reasontherefor is to obtain a sulfide solid electrolyte material with highchemical stability. The proportion of the anion structure of theortho-composition among the total anion structures in the ion conductoris preferably 70 mol % or more, and more preferably 90 mol % or more.The proportion of the anion structure of the ortho-composition may bedetermined by, for example, a Raman spectroscopy, a NMR, and an XPS.

In addition to the ion conductor, the sulfide solid electrolyte materialmay include a lithium halide. Examples of the lithium halide may includeLiF, LiCl, LiBr, and LiI, and among them, LiCl, LiBr, and LiI arepreferable. The proportion of LiX (X═I, Cl, Br) in the sulfide solidelectrolyte material is, for example, within a range of 5 mol % to 30mol %, and may be within a range of 15 mol % to 25 mol %.

The solid electrolyte material may be a crystalline material, and may bean amorphous material. Also, the solid electrolyte material may be aglass, and may be a crystallized class (a glass ceramic). Examples ofthe shape of the solid electrolyte material may include a granularshape.

Examples of the conductive material may include carbon materials such asacetylene black (AB), Ketjen black (KB), carbon fiber, carbon nanotube(CNT), and carbon nanofiber (CNF). Also, examples of the binder mayinclude rubber based binders such as butylene rubber (BR),styrene-butadiene rubber (SBR); and fluoride based binders such aspolyvinylidene fluoride (PVDF).

The thickness of the anode active material layer is, for example, withina range of 0.1 μm to 300 μm, and may be within a range of 0.1 μm to 100μm.

(2) Cathode Active Material Layer

The cathode active material layer includes at least a cathode activematerial, and may include at least one of a solid electrolyte material,a conductive material, and a binder as required.

The cathode active material is not particularly limited, and examplesthereof may include an oxide active material. Examples of the oxideactive material may include a rock salt bed type active material such asLiCoO₂, LiMnO₂, LiNiO₂, LiVO₂, and LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂; aspinel type active material such as LiMn₂O₄, Li₄Ti₅O₁₂, andLi(Ni_(0.5)Mn_(1.5))O₄; and an olivine type active material such asLiFePO₄, LiMnPO₄, LiNiPO₄, and LiCoPO₄. Also, as the oxide activematerial, for example, a LiMn spinel active material represented byLi_(1+x)Mn_(2−x−y)M_(y)O₄ (M is at least one kind of Al, Mg, Co, Fe, Ni,and Zn, and 0<x+y<2), and a lithium titanate may be used.

Also, on a surface of the cathode active material, a coating layerincluding a Li ion conductive oxide may be formed. The reason thereforeis to suppress the reaction between the cathode active material and thesolid electrolyte material. Examples of the Li ion conductive oxide mayinclude LiNbO₃, Li₄Ti₅O₁₂, and Li₃PO₄. The thickness of the coatinglayer is, for example, within a range of 0.1 nm to 100 nm, and may bewithin a range of 1 nm to 20 nm. The coverage of the coating layer onthe cathode active material surface is, for example, 50% or more, andmay be 80% or more.

The solid electrolyte material, the conductive material, and the binderused for the cathode active material layer are respectively in the samecontents as those described in “(1) Anode active material layer” above;thus, the descriptions herein are omitted. Also, the thickness of thecathode active material layer is, for example, within a range of 0.1 μmto 300 μm, and may be within a range of 0.1 μm to 100 μm.

(3) Solid Electrolyte Layer

The solid electrolyte layer is a layer formed between the cathode activematerial layer and the anode current collector. Also, the solidelectrolyte layer includes at least a solid electrolyte material, andmay further include a binder as required. The solid electrolyte materialand the binder used for the solid electrolyte layer are respectively inthe same contents as those described in “(1) Anode active materiallayer” above; thus, the descriptions herein are omitted.

The content of the solid electrolyte material in the solid electrolytelayer is, for example, within a range of 10% by weight to 100% byweight, and may be within a range of 50% by weight to 100% by weight.Also, the thickness of the solid electrolyte layer is, for example,within a range of 0.1 μm to 300 μm, and may be within a range of 0.1 μmto 100 μm.

(4) Cathode Current Collector and Anode Current Collector

The cathode current collector collects currents of the above describedcathode active material layer, and the anode current collector collectscurrents of the above described anode active material layer. The metalelement included in the cathode current collector is not particularlylimited, and examples thereof may include Al, Fe, Ti, Ni, Zn, Cr, Au,and Pt. The cathode current collector may be a simple substance of themetal element, and may be an alloy including the metal element as themain component. Stainless steel (SUS) is an example of the Fe alloy, andSUS304 is preferable.

Examples of the shape of the cathode current collector may include afoil shape and a mesh shape. The thickness of the cathode currentcollector is, for example, 0.1 μm or more, and may be 1 μm or more. Whenthe cathode current collector is too thin, the current collectingfunction may be degraded. Meanwhile, the thickness of the cathodecurrent collector is, for example, 1 mm or less, and may be 100 μm orless. When the cathode current collector is too thick, the energydensity of a battery may be degraded.

The metal element included in the anode current collector is notparticularly limited, and examples thereof may include Cu, Fe, Ti, Ni,Zn, and Co. The anode current collector may be a simple substance of themetal element, and may be an alloy including the metal element as themain component. Stainless steel (SUS) is an example of the Fe alloy, andSUS304 is preferable.

Examples of the shape of the anode current collector may include a foilshape and a mesh shape. The thickness of the anode current collector is,for example, 0.1 μm or more, and may be 1 μm or more. When the anodecurrent collector is too thin, the current collecting function may bedegraded. Meanwhile, the thickness of the anode current collector is,for example, 1 mm or less, and may be 100 μm or less. When the anodecurrent collector is too thick, the energy density of a battery may bedegraded.

Incidentally, the present disclosure is not limited to the embodiments.The embodiments are exemplification, and any other variations areintended to be included in the technical scope of the present disclosureif they have substantially the same constitution as the technical ideadescribed in the claim of the present disclosure and offer similaroperation and effect thereto.

EXAMPLES

The present disclosure will be described in more details. First, in eachof Reference Examples 1 and 2, it was confirmed that the unevenness ofshort circuit resistance among a plurality of cells in a conventionalstacked battery was large.

Reference Example 1 Production of Cathode

Using a tumbling fluidized bed granulating-coating machine (manufacturedby Powrex Corp.), the cathode active material(Li_(1.15)Ni_(1/3)Co_(1/3)Mn_(1/3)W_(0.005)O₂) was coated with LiNbO₃ inthe atmospheric environment. After that, by burning thereof in theatmospheric environment, a coating layer including LiNbO₃ was formed onthe surface of the cathode active material. Thereby, a cathode activematerial having the coating layer on the surface thereof was obtained.

Next, butyl butyrate, 5% by weight butyl butyrate solution of a PVDFbased binder (manufactured by Kureha Corp.), the obtained cathode activematerial, a sulfide solid electrolyte material (Li₂S—P₂S₅ based glassceramic including LiI and LiBr, average particle size D₅₀=0.8 μm), and aconductive material (a vapor-grown carbon fiber, VGCF, manufactured byShowa Denko K. K.) were added into a propylene (PP) container so as tobe cathode active material:sulfide solid electrolyte material:conductivematerial:binder=85:13:1:1 in the weight ratio. Next, the PP containerwas stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50,manufactured by SMT Corp.) Next, the PP container was agitated for 3minutes by an agitation mixer (TTM-1, manufactured by Sibata ScientificTechnology LTD.), and further, was stirred for 30 seconds by theultrasonic dispersion apparatus to obtain a coating solution.

Next, an Al foil (manufactured by Nippon Foil Mfg. Co. Ltd., a cathodecurrent collector) was prepared. The obtained coating solution waspasted on the Al foil by a blade method using an applicator. The coatedelectrode was dried naturally, and then, was dried at 100° C. for 30minutes on a hot plate to form a cathode active material layer on onesurface of the cathode current collector. Next, the obtained product wascut according to the size of the battery to obtain a cathode.

Production of Anode

Butyl butyrate, 5% by weight butyl butyrate solution of a PVDF basedbinder (manufactured by Kureha Corp.), an anode active material(silicon, manufactured by Kojundo Chemical Lab. Co., Ltd., averageparticle size D₅₀=5 μm), a sulfide solid electrolyte material (Li₂S—P₂S₅based glass ceramic including LiI and LiBr, average particle sizeD₅₀=0.8 μm), and a conductive material (a vapor-grown carbon fiber,VGCF, manufactured by Showa Denko K. K.) were added into a PP containerso as to be anode active material:sulfide solid electrolytematerial:conductive material:binder=55:42:2:1 in the weight ratio. Next,the PP container was stirred for 30 seconds by an ultrasonic dispersionapparatus (UH-50, manufactured by SMT Corp.). Next, the PP container wasagitated for 30 minutes by an agitation mixer (TTM-1, manufactured bySibata Scientific Technology LTD.), and further, was stirred for 30seconds by the ultrasonic dispersion apparatus to obtain a coatingsolution.

Next, as shown in FIG. 8A, a Cu foil (anode current collector 5) wasprepared. The obtained coating solution was pasted on the Cu foil by ablade method using an applicator. The coated electrode was driednaturally, and then, was dried at 100° C. for 30 minutes on a hot plate.Thereby, as shown in FIG. 8B, anode active material layer 2 was formedon one surface of the Cu foil (anode current collector 5). After that,by the similar treatment, anode active material layer 2 was formed onanother surface of the Cu foil (anode current collector 5) as shown inFIG. 8C. Next, the obtained product was cut according to the size of thebattery to obtain an anode.

Production of Solid Electrolyte Layer

Heptane, 5% by weight heptane solution of a butylene rubber based binder(manufactured by JSR Corp.), and a sulfide solid electrolyte material(Li₂S—P₂S₅ based glass ceramic including LiI and LiBr, average particlesize D₅₀=2.5 μm) were added into a PP container. Next, the PP containerwas stirred for 30 seconds by an ultrasonic dispersion apparatus (UH-50,manufactured by SMT Corp.). Next, the PP container was agitated for 30minutes by an agitation mixer (TTM-1, manufactured by Sibata ScientificTechnology LTD.), and further, was stirred for 30 seconds by theultrasonic dispersion apparatus to obtain a coating solution.

Next, an Al foil (manufactured by Nippon Foil Mfg. Co. Ltd.) wasprepared. The obtained coating solution was pasted on the Al foil by ablade method using an applicator. The coated electrode was driednaturally, and then, was dried at 100° C. for 30 minutes on a hot plate.Next, the obtained product was cut according to the size of the batteryto obtain a transfer member including the Al foil and the solidelectrolyte layer.

Production of Evaluation Battery

Each of the two obtained transfer members was placed on the anode activematerial layers formed on the both sides of the anode current collector,and the product was pressed under the pressure of 4 ton/cm² by a coldisostatic pressing method (CIP method). After that, the Al foils of thetransfer members were peeled off. Thereby, as shown in FIG. 8D, solidelectrolyte layers 3 were formed on anode active material layers 2.Next, each of the two above obtained cathodes was placed on the solidelectrolyte layers formed on the both sides of the anode currentcollectors, and the product was pressed under the pressure of 4 ton/cm²by the cold isostatic pressing method (CIP method). Thereby, as shown inFIG. 8E, cathode active material layers 1 and cathode current collectors4 were formed on solid electrolyte layers 3. As described above, atwo-stacked cell was obtained. Further, 30 of the obtained two-stackedcells were stacked, and the obtained product was sealed with an aluminumlaminate film to obtain an evaluation battery.

Reference Example 2 Production of Anode

Butyl butyrate, 5% by weight butyl butyrate solution of a PVDF basedbinder (manufactured by Kureha Corp.), an anode active material (naturalgraphite, manufactured by Nippon Carbon Co., Ltd., average particle sizeD₅₀=10 μm), and a sulfide solid electrolyte material (Li₂S—P₂S₅ basedglass ceramic including LiI and LiBr, average particle size D₅₀=0.8 μm)were added into a PP container so as to be anode active material:sulfidesolid electrolyte material:binder=59:40:1 in the weight ratio. Next, thePP container was stirred for 30 seconds by an ultrasonic dispersionapparatus (UH-50, manufactured by SMT Corp.) Next, the PP container wasagitated for 30 minutes by an agitation mixer (TTM-1, manufactured bySibata Scientific Technology LTD.), and further, was stirred for 30seconds by the ultrasonic dispersion apparatus to obtain a coatingsolution.

Production of Evaluation Battery

A two-stacked cell was obtained in the same manner as in ReferenceExample 1 except that the obtained coating solution was used. Further,an evaluation battery was obtained in the same manner as in ReferenceExample 1 except that 40 of the obtained two-stacked cells were stacked.

Evaluation

A nail penetration test was conducted for each evaluation batteryobtained in Reference Examples 1 and 2 under the following conditions.

Charging status: uncharged

Resistance meter: RM3542 manufactured by Hioki E. E. Corp.

Nail: SK (carbon tool steel) material (ϕ: 8 mm, tip angle: 60°)

Speed of the nail: 25 mm/sec

The short circuit resistance of a cell was obtained from a voltageprofile upon the nail penetration. An example of the voltage profile isshown in FIG. 9. As shown in FIG. 9, the voltage of the cell decreasesby penetrating the nail. Here, the initial voltage is referred to as V₀,and the minimum voltage upon the nail penetration is referred to as V.Also, the internal resistance of the cell was measured in advance, andthe internal resistance is referred to as r. Also, the short circuitresistance of the cell is referred to as R. When presuming that all ofthe current generated due to the voltage drop upon the nail penetrationis the short circuit current, a relationship of V/R=(V₀−V)/r isestablished. The short circuit resistance R of the cell may becalculated from this relationship. By compiling the voltage profile ofeach cell, a variation of the short circuit resistance in the thicknessdirection was confirmed. The results thereof are shown in Table 2 andTable 3. Incidentally, the values of the short circuit resistance inTable 2 and Table 3 are relative values when the short circuitresistance of the 1^(st) cell is 1. Also, the cell close to the nailpenetration surface was numbered as the 1^(st) cell.

TABLE 2 <Si> Short circuit N^(th) cell resistance 1 1 10 0.005 20 2885930 38255 40 671141 50 18121 60 0.026

TABLE 3 <C> Nth Short circuit cell resistance 1 1 10 0.159 40 0.968 603.683 80 0.698

As shown in Table 2 and Table 3, in both Reference Examples 1 and 2, theshort circuit resistance of the 1^(st) cell was more than the shortcircuit resistance of the 10^(th) cell. The reason therefor is presumedthat upon the nail penetration, the insulating part of the laminate filmwas dragged in. Also, in Reference Example 1, the short circuitresistance of the 40^(th) cell was more compared to the short circuitresistance of the 1^(st) cell or the 10^(th) cell, and in ReferenceExample 2, the short circuit resistance of the 60^(th) cell was morecompared to the short circuit resistance of the 1^(st) cell or the10^(th) cell. As described above, the short circuit resistance was lessin the surface-side cell, and was more in the center-side cell.Particularly, in Reference Example 1 in which Si was used as the anodeactive material, the unevenness of the short circuit resistance wasextremely large compared to Reference Example 2 in which C was used asthe anode active material.

REFERENCE SIGNS LIST

-   1 cathode active material layer-   2 anode active material layer-   3 solid electrolyte layer-   4 cathode current collector-   5 anode current collector-   10 cell-   100 stacked battery-   110 nail

What is claimed is:
 1. A stacked battery comprising: a plurality of cells in a thickness direction, wherein the plurality of cells are electrically connected in parallel; each of the plurality of cells includes a cathode current collector with a cathode current collecting tab, a cathode active material layer, a solid electrolyte layer, an anode active material layer, and an anode current collector with an anode current collecting tab, in this order; the stacked battery includes a surface-side cell that is located on a surface side of the stacked battery, and a center-side cell that is located on a center side rather than the surface-side cell; an area in plan view of the cathode current collecting tab in the surface-side cell is less than an area in plan view of the cathode current collecting tab in the center-side cell; and the surface-side cell and the center-side cell satisfy at least one of: condition i) a resistance of the cathode current collecting tab in the surface-side cell is more than a resistance of the cathode current collecting tab in the center-side cell; and condition ii) a resistance of the anode current collecting tab in the surface-side cell is more than a resistance of the anode current collecting tab in the center-side cell.
 2. The stacked battery according to claim 1, wherein a specific resistance of the cathode current collecting tab in the surface-side cell is more than a specific resistance of the cathode current collecting tab in the center-side cell.
 3. The stacked battery according to claim 1, wherein a specific resistance of the anode current collecting tab in the surface-side cell is more than a specific resistance of the anode current collecting tab in the center-side cell.
 4. The stacked battery according to claim 1, wherein a thickness of the cathode current collecting tab in the surface-side cell is less than a thickness of the cathode current collecting tab in the center-side cell.
 5. The stacked battery according to claim 1, wherein a thickness of the anode current collecting tab in the surface-side cell is less than a thickness of the anode current collecting tab in the center-side cell.
 6. The stacked battery according to claim 1, wherein an area of the anode current collecting tab in the surface-side cell is less than an area of the anode current collecting tab in the center-side cell.
 7. The stacked battery according to claim 1, wherein the cathode current collecting tab in the surface-side cell includes a resistor on at least one surface side.
 8. The stacked battery according to claim 1, wherein the anode current collecting tab in the surface-side cell includes a resistor on at least one surface side.
 9. The stacked battery according to claim 1, wherein an area of a welded portion in contact with the cathode current collecting tab in the surface-side cell is less than an area of a welded portion in contact with the cathode current collecting tab in the center-side cell.
 10. The stacked battery according claim 1, wherein an area of a welded portion in contact with the anode current collecting tab in the surface-side cell is less than an area of a welded portion in contact with the anode current collecting tab in the center-side cell.
 11. The stacked battery according to claim 1, wherein, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥3, in order along the thickness direction of the stacked battery, the surface-side cell is a cell that belongs to a cell region A including 1^(st) cell to (N/3)^(th) cell.
 12. The stacked battery according to claim 11, wherein the center-side cell is a cell that belongs to a cell region B including ((N/3)+1)^(th) cell to (2N/3)^(th) cell.
 13. The stacked battery according to claim 12, wherein an average resistance of the cathode current collecting tab in the cell region A is more than an average resistance of the cathode current collecting tab in the cell region B.
 14. The stacked battery according to claim 12, wherein an average resistance of the anode current collecting tab in the cell region A is more than an average resistance of the anode current collecting tab in the cell region B.
 15. The stacked battery according to claim 1, wherein, when each of the plurality of cells is numbered as 1^(st) cell to N^(th) cell, in which N≥60, in order along the thickness direction of the stacked battery, the surface-side cell is a cell that belongs to a cell region C including 1^(st) cell to 20^(th) cell.
 16. The stacked battery according to claim 15, wherein the center-side cell is a cell that belongs to a cell region D including 21^(st) cell to 40^(th) cell.
 17. The stacked battery according to claim 16, wherein an average resistance of the cathode current collecting tab in the cell region C is more than an average resistance of the cathode current collecting tab in the cell region D.
 18. The stacked battery according to claim 16, wherein an average resistance of the anode current collecting tab in the cell region C is more than an average resistance of the anode current collecting tab in the cell region D.
 19. The stacked battery according to claim 1, wherein the anode active material layer includes Si or a Si alloy as an anode active material. 